Nonionic water soluble cellulose ethers are employed in a wide variety of industrial applications, as thickeners, as water retention aids, and as suspension aids in certain polymerization processes, among others. Widely used, commercially available, nonionic cellulose ethers include methylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, hydroxyethylpropylcellulose, hydroxypropylcellulose, and ethylhydroxyethylcellulose.
As is generally the case with high polymers, better thickening efficiency is realized with higher molecular weight cellulose ethers. U.S. Pat. Nos. 4,228,277 and 4,243,802 (Landoll) disclose nonionic cellulose ethers of relatively low molecular weight which are capable of producing viscous aqueous solutions in practical concentrations. U.S. Pat. No. 4,845,175 discloses alkylaryl hydrophobically modified hydroxyethylcellulose as a useful material for emulsion polymerization, but contains no disclosure of how to make or use the compounds of the present invention. These products exhibit a relatively high degree of surface activity compared to that of more conventional nonionic water soluble cellulose ethers. These products are nonionic cellulose ethers which are modified by substitution with specified amounts of C.sub.10 to C.sub.24 alkyl radicals. Such ethers are substituted with an amount of long chain alkyl hydrocarbon radical between about 0.2 weight percent and the amount which renders said cellulose ether less than 1% by weight soluble in water. The base cellulose ether thus modified is preferably one of low to medium molecular weight, i.e., less than about 800,000 and preferably between 20,000 and 500,000, or a Degree of Polymerization (D.P.) of about 75 to 1,800.
Modification of the cellulose ethers with small hydrophobic groups such as ethyl, benzyl and phenylhydroxyethyl groups were not found to effect the property improvements shown by the long chain alkyl hydrophobic modifications. The long chain alkyl cellulose ethers disclosed were useful as stabilizers in emulsion polymerizations, as thickeners in cosmetics, and as flocculants in mineral processing. One particularly good utility was as a thickener in latex paint, where very small amounts of low molecular weight long chain alkyl modified nonionic cellulose ethers outperformed larger quantities of higher molecular weight conventional nonionic cellulosic ethers. The advantages of these products in this particular use are discussed in detail in the Aqualon publication entitled "Natrosol.RTM. Plus-Modified Hydroxyethylcellulose-Performance as a Latex Paint Thickener." Specifically, they provide improved paint rheology, excellent spatter resistance, and good thickening efficiency in a wide variety of latex paint formulations. Paint leveling properties are adequate and better than those obtained with the unmodified base polymer from which they were prepared. However, further improvement in leveling properties would be desirable.